My question is: can I use a Fluke 179 Digital Multimeter to verify the "actual" amount of stored coulombs in a capacitor at a certain voltage. If so, how do I do it. I need to do this to verify my calculations and to verify the tolarances of the capacitor used in my experiments. Thanks for any help
Can I use a Dig. Multimeter to calculate coulombs.
- Thread starter bradlee
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sparky_magoo
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Re: Can I use a Dig. Multimeter to calculate coulombs.
bradlee,
Your Fluke has no way of knowing how many coulombs are stored in your capacitor. The Fluke can only measure the EMF potential between the capacitors two leads.
bradlee,
Your Fluke has no way of knowing how many coulombs are stored in your capacitor. The Fluke can only measure the EMF potential between the capacitors two leads.
Re: Can I use a Dig. Multimeter to calculate coulombs.
You may be able to make a rough measurement of the charge using a DMM and another low-leakage capacitor of known value. See this
web page about electrostatic apparatus.
Look around on the Keithley Instruments web site and in their Low Level Measurements Handbook, and you'll find more information on charge measurement.
You may be able to make a rough measurement of the charge using a DMM and another low-leakage capacitor of known value. See this
web page about electrostatic apparatus.
Look around on the Keithley Instruments web site and in their Low Level Measurements Handbook, and you'll find more information on charge measurement.
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Re: Can I use a Dig. Multimeter to calculate coulombs.
I don't understand why you are asking this question again. What is different from the question you asked in this thread?
Measure the voltage, multiply by the capacitance, and you will get the stored charge.
What exactly are you looking for?
I don't understand why you are asking this question again. What is different from the question you asked in this thread?
Measure the voltage, multiply by the capacitance, and you will get the stored charge.
What exactly are you looking for?
Re: Can I use a Dig. Multimeter to calculate coulombs.
bradlee,
Yes, you can determine charge, Q, on a cap with a high impedance voltmeter. You must know the value of the cap however.
Q = CxV
units are Coulombs, Farads, and Volts
Also, the impedance of the meter will bleed off the charge exponentially, and a leaky cap will also bleed off the charge. This method will not work for small values of capacitance, and you have to be quick with larger caps.
bradlee,
Yes, you can determine charge, Q, on a cap with a high impedance voltmeter. You must know the value of the cap however.
Q = CxV
units are Coulombs, Farads, and Volts
Also, the impedance of the meter will bleed off the charge exponentially, and a leaky cap will also bleed off the charge. This method will not work for small values of capacitance, and you have to be quick with larger caps.
P
Physis 2
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Re: Can I use a Dig. Multimeter to calculate coulombs.
Charlie, it's my fault. I insisted he wont be able to get an accurate value without insuring he knows what the capacitance "actually" is.
Edit: I think he's after the actual capacitance now.
[ October 05, 2005, 08:34 PM: Message edited by: Physis 2 ]
Charlie, it's my fault. I insisted he wont be able to get an accurate value without insuring he knows what the capacitance "actually" is.
Edit: I think he's after the actual capacitance now.
[ October 05, 2005, 08:34 PM: Message edited by: Physis 2 ]
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